1. Field of the Invention
The invention relates to a method and a system for updating digital road maps which are used in particular for traffic direction and guiding vehicles to their destinations. In the method, actual route data is determined, stored and transmitted to a traffic computer by at least one test vehicle provided for that purpose. The traffic computer evaluates the information items contained in the route data and assigns them as attributes to the corresponding road sections of a digital road map.
2. Description of the Prior Art
From "ISATA--26th International Symposium on Automotive Technology and Automation", Aachen, Sep. 13-17, 1993, an interactive, dynamic road guidance system ("EURO-SCOUT" project) is known, in which specially equipped vehicles exchange messages with a traffic computer (control computer). The duplex communication is carried out in this case via beacons equipped with an infrared transmitting/receiving device, which are set up at all the important junction points of the road network. The vehicles, which are likewise equipped with a transmitting/receiving device, receive from the traffic computer via the beacons inter alia actual information items about the shortest routes to a desired destination. The main information source of the traffic computer is test vehicles which move and "swim along" with and in the traffic flow. These vehicles transmit to the traffic computer in particular their travel times between important traffic junction points, as well as waiting times at light signal installations. These information items are subsequently used by the traffic computer for road guidance and traffic direction, by, for instance, transmitting appropriate traffic control information items to the vehicles to be guided and outputting them via a control device on a display (for example one known from DE-A 4039887) in the vehicle.
In the case of this system, it is important that the traffic computer must already have an up-to-date road map for successful route guidance. This map includes the knowledge of specific properties of the individual road sections of the road network, which are designated below as attributes and can in particular comprise the ability to drive in a direction (one way streets), permissible vehicle height or vehicle width or vehicle weight and other such information items, and are widely indicated in the form of appropriate traffic signs. The updating of the road map is normally carried out by previous information items being obtained from appropriate state or municipal institutions or the road sections being regularly driven by special vehicles and changes being noted on the road map. Regularly driving the road network, however, represents a considerable effort in terms of personnel and economy, especially in large towns, since it is generally necessary to register beforehand all the facts which are subsequently intended to be checked by the operating personnel of the vehicle during driving over the roads of the road network.
In spite of this, deviations between the entries in the digital road map and the real situation in the road network repeatedly occur with respect to the ability to drive over road sections and permissible changes of direction at crossings and junctions, since as a rule it is not possible to check all the roads of the road network on one day although road blockages may have resulted, for example from construction work. Added to this is the fact that the personnel employed do not always work faultlessly, even given appropriate technical preconditions. However, in the case of an automated, computer controlled destination guidance, route planning and traffic direction system, faulty guidance to destinations, caused by a faulty road map, must be able to be excluded with a very high certainty. This quality criterion has as a consequence a distinctly higher priority than, for example, guidance to a destination along the shortest route. A slightly longer way is more easily tolerated than a forced turning maneuver because of the inability to drive over a road section.